1. Field of the Invention
The present invention relates to a relief technique for a redundant memory in a semiconductor device, and more particularly to, a technique for efficiently transferring relief information in a system in which information for relieving a defective cell is generated by an operation of a test circuit built in a chip.
2. Description of the Related Art
Conventionally, a method has been proposed in which, when a defect is present in a memory, information for avoiding the defective portion is extracted by an operation of a test circuit built in a chip, and based on the information, a fuse element or the like is blown out (see, for example, Patent Document 1).
Patent Document 1: JP 6-84393 A
Recently, system LSIs have had large scales, and the capacity and the number of memories provided on a chip tend to be increased. Therefore, the number of redundant memories provided on a chip is more and more increased, and therefore, the area of test circuits for testing the redundant memories is expected to be increased.
To suppress an increase in the test circuit area, it is effective to suppress the number of test circuits and increase the number of redundant memories which are to be tested by one test circuit. Note that, when one test circuit tests a large number of redundant memories, it is necessary to efficiently transfer information for relieving a defective cell, i.e., relief information.
However, a method for transferring relief information is not specifically indicated in the conventional art. For example, Patent Document 1 only describes a configuration in which information for cutting a fuse which is required to relieve any redundant memory is transferred in parallel (FIG. 2 therein illustrating an example). When the relief information is transferred in parallel, a large number of outputs of a test circuit need to be provided, and in addition, a large number of conductors which serve as transfer channels for relief information need to be provided. Therefore, the circuit area is disadvantageously increased, so that a problem arises.